1. Field of the Invention
The present invention relates to the field of telephone line communication devices.
2. Prior Art
Communication devices for data communication over telephone lines are well known in the prior art. Typically such devices utilize some form of modem to modulate serial digital data into the frequency pass band of telephone systems for transmission, and to demodulate a corresponding received signal for recovery of the digital data at the receiving end. Such communication capability may be in a single direction at any one time (half duplex) or may include simultaneous bidirectional capabilities (full duplex). Using such communication techniques, various devices have been coupled to telephone lines for various purposes. By way of example, modems have been used to couple personal computers through telephone lines, generally for the purpose of data communication with other similar computers. In general such devices have not included a handset for voice communication and also such systems are relatively bulky, and accordingly they are generally limited to use for point-to-point data communications. In other instances, modems have been used for data communications over telephone lines between a central computer and one or more remote terminals specially configured for such use. While such terminals may include a full keyboard for data entry purposes, and a display for displaying entered and transmitted information, such terminals are generally limited in function and purpose to data entry and communication tasks and do not themselves provide any substantial form of self control or ability to control other devices.
One form of general purpose electronic telephone station is shown in U.S. Pat. No. 4,291,198. That device or system is microprocessor based and includes a handset, a video output display screen and a full alphanumeric key set, the keys being arranged generally as a normal "qwerty" organization but in an orthogonal array rather than in a conventional typewriter keyboard layout. The microprocessor based system allows various forms of control of the station set, though as with other prior art telephone line communication devices, it too is dedicated in purpose to communication, having the added feature of voice communication capabilities. Also the system of that patent utilizes a conventional telephone handset and a cathode ray tube display, having a substantially square display area. Accordingly the system is relatively large and not suitable for use as a portable device.